<style>

    div{
        border-radius: 20px;
        width: 70%;
        height: 400px;
        margin:  50 auto;
        background: repeating-linear-gradient(
            45deg,
            yellow 0px,
            yellow 40px,
            black 40px,
            black 80px
        );
    }

</style>

<div></div>